This invention relates to a connecting element for detachably connecting sectional bars of a structural framework to one another.
In a structural framework assembly comprising various sectional bars or extrusions, at least some of the sectional bars, called "support profiles," have undercut longitudinal slots, while other sectional bars, called "edge profiles," are hollow profiles and accept a connecting element at an end face. The connecting element or lock consists of a housing, in which a mounting element is slidably disposed. The mounting element has at one end a single connecting hook projecting from an end face of the housing and is movable in a longitudinal direction by means of an eccentric pin which traverses an aperture in the mounting element. The eccentric pin has a handle or actuating end held, resiliently detented, in a transverse hole of the profile bar containing the connecting element, the actuating end of the eccentric pin being pushed out of the housing, in the manner of a pushbutton, and held in the hole of the profile bar by a spring engaging a side of the mounting element opposite the actuating end of the eccentric pin. The housing is provided on an inner surface with an incline engageable with a counter-incline or bent segment formed on the mounting element.
Various embodiments of such connecting elements are known and used in particular in the assembly of racks which are used in the construction of showrooms, stores or the like. The joint between a support profile and an edge profile coupled thereto by a connecting element should be extremely strong, on the one hand, but, on the other hand, should also be easy to assembly and disassemble.
As described in U.S. Pat. No. 4,455,103, one embodiment of a connecting element comprises a unitary support housing having a rising wedge surface on an inner surface of the housing and a mounting element which can be moved lengthwise within the housing, the mounting element taking the form of a strip of steel sheet which has a counter-incline or bent portion which is pushed against the wedge surface of the housing by the force of a spring integral with the mounting strip. At an end face of the housing, two coupling projections are firmly arranged, between which the mounting element moves, the mounting element and the coupling projectings resting, upon completion of a clamping operation, against opposite sides of a longitudinal slot in a support section. The mounting element can be moved longitudinally relative to the lock by an eccentric pin, the mounting element executing not only a longitudinal motion but, by a camming engagement of the wedge-shaped incline in the housing with the bent portion of the mounting element, also a transverse motion. Through these motion components, occurring simultaneously, a particular secure and strong connection of two profile bars is to be achieved according to the teachings of U.S. Pat. No. 4,455,103.
The principles underlying the structure and operation of the connecting element of U.S. Pat. No. 4,445,103 had been previously disclosed in German Utility Model DE-GM No. 7341203. Improvements introduced by U.S. Pat. No. 4,455,103 were made with the objects of simplifying the structure of the connecting element, facilitating assembly and disassembly and providing for convenient insertion and, if necessary, removal of the connecting element from the sectional bars. It has been found that the assembly and disassembly of the connecting elements disclosed in U.S. Pat. No. 4,455,103 can present considerable difficulties. For example, the eccentric pin as well as the mounting element consisting of a strip of steel sheet metal must be introduced into the housing through an end face thereof. The insertion of the mounting element is not simple, because the spring tab formed from the sheet metal strip must be pushed against the body of the mounting element for the introduction to occur. In addition, a multiplicity of windows as well as inclined surfaces and ramps must be formed on the side walls of the housing to enable assembly and disassembly of the connecting element.
Because two mutually perpendicular motion cycles take place in a connecting element during the coupling operation proper, i.e., during engagement of a hook on the mounting element with an inwardly facing surface at a longitudinal slot in a support profile, shearing forces occur which on the one hand stress the profile bars additionally and, on the other hand, can lead to an unintended release of the connection.
An object of the present invention is to provide an improved connecting element of the above-described type.
Another, more particular, object of the present invention is to provide such a connecting element which is easy to manufacture.
Another particular object of the present invention is to provide such a connecting element which forms a secure, heavily stressable connection between sectional bars, which connection can not be broken unintentionally.
Yet another object of the present invention is to provide such a connecting element in which the coupling operation gives rise to reduced stresses and strains and whereby the connected profile bars are stressed as little as possible.